The present invention relates to ablation therapy planning, and more particularly to patient-specific simulation of tissue ablation using medical imaging data.
In spite of recent advances in cancer therapy, treatment of primary and metastatic tumors of the abdomen, including the liver, remains a significant challenge. Hepatocellular carcinoma (HCC) for example is one of the most common malignancies encountered throughout the world (more than 1 million cases per year), with increasing frequency in western countries due to the changing prevalence of hepatitis C. For both primary liver cancer and hepatic metastases, liver resection (partial hepatectomy) is the current preferred option in patients having confined disease. In selected cases of early HCC, total hepatectomy with liver transplantation may also be considered. Unfortunately, less than 25% of patients with primary or secondary liver cancer are candidates for resection or transplantation, primarily due to tumor type, location, or underlying liver disease. Consequently, increasing interest has been focused on ablative approaches for the treatment of unresectable liver tumors or for patients not suitable for surgery. Rather than extirpation, this technique uses local in situ tumor destruction. A variety of methods have been employed to locally ablate tissue. Radiofrequency ablation (RFA) is the most commonly used, but other techniques are also used, including ethanol injection, cryo-therapy, irreversible electroporation, and microwave ablation.
The RFA procedure is performed by placing a probe within or near the malignant tissue. Electrodes at the tip of the probe create heat, which is conducted into the surrounding tissue, causing coagulative necrosis at temperatures above 50° C. In order to prevent recurrence, the RFA procedure is considered to be successful if the generated necrosis area fully covers the tumor. To place the probe at the target location, the physician relies on intra-operative imaging techniques, such as ultrasound. However, the success of the procedure depends on the optimal placement of the probe and heat delivery with respect to the circulation system and tissue properties of the liver and tumors. The success of ablation is further challenged by the hepatic blood vessels that dissipate heat, thus potentially reducing RFA efficiency. Different placements may have different results, and it is sometimes necessary to combine successive ablations for an optimal procedure.